diff --git a/01-the-very-basics/hello-world.mps b/01-the-very-basics/01-hello-world.mps
similarity index 100%
rename from 01-the-very-basics/hello-world.mps
rename to 01-the-very-basics/01-hello-world.mps
diff --git a/01-the-very-basics/hello-world-in-a-loop.mps b/01-the-very-basics/02-hello-world-in-a-loop.mps
similarity index 100%
rename from 01-the-very-basics/hello-world-in-a-loop.mps
rename to 01-the-very-basics/02-hello-world-in-a-loop.mps
diff --git a/01-the-very-basics/hello-world-in-another-loop.mps b/01-the-very-basics/03-hello-world-in-another-loop.mps
similarity index 100%
rename from 01-the-very-basics/hello-world-in-another-loop.mps
rename to 01-the-very-basics/03-hello-world-in-another-loop.mps
diff --git a/01-the-very-basics/hello-world-in-a-nested-loop.mps b/01-the-very-basics/04-hello-world-in-a-nested-loop.mps
similarity index 100%
rename from 01-the-very-basics/hello-world-in-a-nested-loop.mps
rename to 01-the-very-basics/04-hello-world-in-a-nested-loop.mps
diff --git a/README.md b/README.md
index 4249a1c..e4ca048 100644
--- a/README.md
+++ b/README.md
@@ -42,12 +42,12 @@ The resulting interpreter is located in `/usr/bin/mumps`.
 
 ## 1. The Very Basics
 
-### [`hello-world.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/hello-world.mps)
-    $ mumps 01-the-very-basics/hello-world.mps
+### [`01-hello-world.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/01-hello-world.mps)
+    $ mumps 01-hello-world.mps
     Hello world
 
-### [`hello-world-in-a-loop.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/hello-world-in-a-loop.mps)
-    $ mumps hello-world-in-a-loop.mps
+### [`02-hello-world-in-a-loop.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/02-hello-world-in-a-loop.mps)
+    $ mumps 02-hello-world-in-a-loop.mps
     Hello world
     Hello world
     Hello world
@@ -59,8 +59,8 @@ The resulting interpreter is located in `/usr/bin/mumps`.
     Hello world
     Hello world
 
-### [`hello-world-in-another-loop.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/hello-world-in-another-loop.mps)
-    $ mumps hello-world-in-another-loop.mps
+### [`03-hello-world-in-another-loop.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/03-hello-world-in-another-loop.mps)
+    $ mumps 03-hello-world-in-another-loop.mps
     Hello world
     Hello world
     Hello world
@@ -72,8 +72,8 @@ The resulting interpreter is located in `/usr/bin/mumps`.
     Hello world
     Hello world
 
-### [`hello-world-in-a-nested-loop.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/hello-world-in-a-nested-loop.mps)
-    $ mumps hello-world-in-a-nested-loop.mps 
+### [`04-hello-world-in-a-nested-loop.mps`](https://github.com/programarivm/gpl-mumps-by-example/blob/master/01-the-very-basics/04-hello-world-in-a-nested-loop.mps)
+    $ mumps 04-hello-world-in-a-nested-loop.mps
     1:1 Hello world
     1:2 Hello world
     1:3 Hello world